With rapid development of semiconductor technology, feature sizes of Complementary Metal-Oxide-Semiconductor (CMOS) devices in very large scale integrated circuits are constantly reducing as predicted by Moore Law, and traditional polysilicon gates and silicon dioxide gate dielectrics are facing many technical challenges. For example, starting from the 45 nm technology node and beyond, the silicon dioxide gate dielectric layer has a thickness of several atomic layers, which will incur sharp rises of gate leakage current and power consumption. In addition, the polysilicon gate electrode causes a polysilicon depletion effect and problems such as a too high gate resistance and the like. To this end, high dielectric constant (high-k) gate dielectric and metal gate electrode, which may be introduced to effectively solve these problems associated with CMOS devices, have been successfully applied to the 32 nm technology by Intel Corporation, USA.
However, introduction of high-k gate dielectric/metal gate structure brings some new problems. For example, during the growth of high-k gate dielectric, a silicon dioxide interface inevitably exists between the high-k gate dielectric and the surface of semiconductor substrate. Generally, the interface layer in the high-k gate dielectric/metal gate process has a thickness of about 0.5 to 0.7 nm. However, once CMOS devices enter the 32 nm technology node or beyond, the equivalent gate oxide thickness of the high-k gate dielectric is not more than 0.7 nm or even highly-demanded, and the thickness of the interface layer will be increased during a high temperature annealing in the subsequent process. Therefore, it becomes a difficulty and focus in the art to reduce equivalent oxide thickness of the high-k gate dielectric by optimizing process conditions and/or materials.